No...they shouldn't do that. Did you get a copy of the evaluation? If not...I would ask for one.

Contacting your union rep would be a good idea if you have one.

Next...if it were me...I would read up on disability discrimination, the ADA, and possibly (if you feel it warrants it) contact the EEOC. If they are making you feel uncomfortable or trying to get rid of you because of your disability...THAT is ILLEGAL.

I know you are mad (I've been there and had to file a charge of disability discrimination against my employer)...but it's very important that you stay professional and calm when you are at work. If you have any additional documentation to support disability discrimination or harassment I would gather that together. Maybe you have emails, previous evaluations prior to the RSD, etc.

Even if you decide not to do anything at this point, arm yourself with knowledge about the law and the proper way to handle these situations. I know in my case I told my employer why I felt what they were doing was wrong and they went ahead and did it anyway. You need to make sure you express your thoughts to your employer...but you have to do it in a calm, professional way. This is really important...don't let them push your buttons and get a rise out of you and give them legit grounds to terminate you.

All that said...I don't know what was in the evaluation or if it would actually be considered discrimination or harassment. But if you feel they are trying to get rid of you...you are probably right. It's always important to take a hard look in the mirror and try to see if there is any truth to what they are saying or if there is something you could do better. Having been a victim of this sort of situation and fought my way out of it, I hope you don't take my saying that the wrong way...it's just good to try and take a step back and really look at the situation from all sides before taking things as far as the situation I just described.

You also need to factor in what you feel would be a good resolution to the situation. If the person performing the evaluation were to change their behavior...would that be enough? This is why it's important to report the situation to the appropriate person/supervisor. If you can document that report in any way (via email or by taking notes at an in person meeting) then so much the better. You need to give your employer the opportunity to correct the situation and make things better. Maybe "they" aren't trying to get rid of you...maybe it's one bad apple or one person who doesn't realize what they are doing or how they are coming across. Give them a chance to fix things and if things don't improve...THEN you can take the next steps. But educate yourself now so you know what to expect and how to proceed. And if you have a union rep who you can discuss these things with then that would be a good idea.

Fingers crossed that you can get this resolved easily and quickly. You don't need the stress of this sort of situation.